1. Field of the Invention
This invention relates to photographic cameras, and, more particularly, to a manually operable or automatic film speed setting system using an electrically conductive marker representative of the sensitivity of film. Still more particularly, it relates to improvements of the film speed setting system in that:
When a cartridge having a marker representative of the sensitivity of film therein is loaded in the camera, the otherwise necessary manipulation of the film speed dial may be overlooked as information representative of film speed is automatically introduced into the computation of an effective exposure value.
The output of the automatic film speed setting means is displayed so that the operator can be made to remember what film speed information is automatically set, not only when the film is transported by a first few frames to obtain a first fresh film frame, but also at a desired point in time when the film is successively advanced for exposure purposes.
Even when a cartridge having the marker is used, the manually operable film speed setting means can be rendered effective as desired.
2. Description of the Prior Art
In setting the given film sensitivity into an exposure control circuit, it has been the prior art practice to operate a film speed dial arranged on the top panel of the camera housing. As a number of films of different sensitivity is accommodated in a single camera, therefore, there is a high possibility for the busy operator of overlooking the necessary manipulation of the film speed dial. This repetition of settings is a very troublesome operation particularly when the operator's concentration is on an object to be photographed.
It is known to provide a film cartridge having a marker representative of the sensitivity of film therein as constructed in the mechanical form adapted for use with an instant type camera or pocket type camera in order to automatically account the sensitivity of film. In cameras having electronic control apparatus, because of the convenience of an electrical signal, this marker has been recently constructed in the form of a number of electrical conductive patches, the combination and permutation of which depend upon the sensitivity of film contained in that cartridge.
So long as the availability of film cartridges having no such markers is universal, it is required that the camera be provided with both the manually operable and the automatic film speed setting means. If the simultaneous use of the manually operable and automatic setting means is not combined with means for selectively introducing the outputs of these setting means into the exposure value computer of the camera in a preferably automatic manner, it is impossible to obtain a correct exposure when the switched position of the film speed dial is left in a position which is different from that for the sensitivity of film as the cartridge having the marker is used.
With the foregoing in mind, the present invention has for the general object to provide a manually operable or automatic film speed setting system which is characterized in that:
(1) When a cartridge having a marker (hereinafter referred to as "Auto-film cartridge") representative of the sensitivity of film therein is loaded in the camera, the exposure value computing circuit accounts for this sensitivity, while the output of the manually operable film speed setting means is automatically cut off from entering said circuit.
(2) The output of the manually operable film speed setting means remains unchanged from the value which occurs just before the Auto-film cartridge is inserted into the camera.
(3) The operator is aware if the Augo-film cartridge is being loaded in the camera.
(4) What film speed is automatically set is displayed.
(5) The film speed display is performed by utilizing the film speed dial in combination with a monitor and safety circuit.
(6) The film speed value display can be established not only during the preparatory transportation of the film in vain, but also at any desired time during the advancements of the film for exposure purposes.
(7) Since a battery check button is utilized in actuating the film speed value display after the preparatory transportation of the film, the use of the Auto-film cartridge leads to the simultaneous display of whether the actual voltage of the electrical power source is above a satisfactory operating level. In addition thereto, the shutter speed and diaphragm aperture value as the exposure determining factor can be displayed when the battery check button is operated.
(8) Even after the Auto-film cartridge is loaded into the camera, it is made possible to change the automatically set film speed to a desired one by use of the film speed dial.